Role of hypothermia in the mechanism of protection against serotonergic toxicity. I. Experiments using 3,4-methylenedioxymethamphetamine, dizocilpine, CGS 19755 and NBQX.

High doses of 3,4-methylenedioxymethamphetamine (MDMA) have been shown to cause long-lasting depletions of central serotonin (5-HT) which are indicative of neuronal toxicity. The noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (DZ) attenuates depletions of 5-HT induced by MDMA. Because DZ has been shown to induce hypothermia in rat models of ischemia, the purpose of this study was to assess whether DZ and two other glutamate antagonists, CGS 19755 (CGS) and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), protect against MDMA-induced 5-HT depletions by induction of hypothermia. Male Sprague-Dawley rats were injected with either saline (SAL), DZ (2.5 mg/kg), CGS (25.0 or 50.0 mg/kg x 2 injections) or NBQX (30.0 mg/kg x 2 injections or 55.0 mg/kg x 3 injections) followed by either MDMA (40.0 mg/kg) or SAL. Core body temperature (TEMP) was monitored for 4 h or longer using radiotelemetry. Base-line TEMP was between 37.0 and 37.6 degrees C. Administration of DZ with MDMA decreased TEMP to 34.0 +/- 0.39 degrees C within 2 h of the MDMA injection, and also protected against serotonergic toxicity. Neither SAL/MDMA nor DZ/SAL had an effect on TEMP over the same period. When rats were treated with DZ/MDMA and TEMP was maintained between 38.4 degrees C and 40.4 degrees C for 4 h, protection against 5-HT depletion was abolished. Coadministration of the competitive NMDA antagonist CGS with MDMA-resulted in a decrease in TEMP to 34.5 +/- 0.27 degrees C, and provided partial protection against 5-HT depletions.(ABSTRACT TRUNCATED AT 250 WORDS)